Marc Fil Daniel

EOM Drivers moved outside PSL enclosure: alog 41852.
OLD/NEW EOM configuration comparison: alog 41435.

We installed the new RF Combiner/amplifier, D1800116, in the EOM driver chains of the 45.5 and 24.1 MHz modulation signals. This replaces the RF power splitter that had poor characteristics. More details in T1800196.

The 24.1 MHz input is connected to an RF distribution amplifier using a 12 dB attenuator. This yields an input signal level of 2.36 dBm. The measured output level is 24.77 dBm. If we include the measured cable loss of 0.43 dB, we infer 24.34 dBm at the EOM. This is a difference of –0.26 dB relative to Koji's setup. The level of the 24.1 MHz signal coming out at the 45.5 MHz input is -19.4 dBm, giving an isolation ratio of about 44 dB.

The 45.5 MHz input is connected directly to the EOM driver. At its maximum setting of 27 dBm, we measure 25.95 dBm towards the EOM. With the measured cable loss of 0.36 dB, we infer 25.59 dBm at the EOM. This is a difference of +1.83 dB relative to Koji's setup.

Using the EOM response from G1800724 of 43 mrad/V and 2.4 mrad/V for the 45.5 and 24.1 MHz modulation signals, we estimate the modulation indices to be 12.5 mrad and 0.259 rad, respectively.

Due to some unexplained and bizarre effect, we see increased broadband noise from the RF combiner output with the frequencies we have, but seem to be ok, if we just move >100 kHz away from the current difference. This requires more investigations.